The present invention relates to a ventilation system for the ventilation and for the aeration of an internal combustion engine. Such ventilation systems are in particular used for the ventilation and the aeration of the crank case of an internal combustion engine. The present invention further relates to a cylinder head cover and an internal combustion engine, which comprise a ventilation system according to the invention.
The ventilation systems mentioned above are in particular, but not only, used for the ventilation of a crank case in internal combustion engines. In the following, the invention is therefore described using the ventilation and aeration of a crank case as an example. For environmental reasons, the blow-by gases occurring there are usually fed back, e.g. to the intake section of the internal combustion engine. To this end, the crank case is ventilated. On the other hand and also for environmental reasons, the pressure in the crank case has to be kept within very tight limits. In order to prevent from an escape of the blow-by gases to the environment, it is for instance not allowed that a positive pressure relative to the atmospheric pressure occurs in the crank case. On the other hand, the crank case pressure may not be lower than a minimum internal pressure, so that under certain operation conditions, where only a small amount of blow-by gases occurs, the crank case even needs an aeration. This means that fresh air is supplied to the crank case. The term ventilation in the sense of this invention has a double meaning. On the one hand, it relates to the release of gases from the crank case. On the other hand, it relates to the total air management in the crankcase.
An aeration of the crank case with fresh air further provides the advantage that the blow-by gases are diluted. It also helps in guiding the blow-by gases from the crank case when only small amounts of these blow-by gases occur. This is of particular importance since nitrogen oxides are present in the blow-by gases, which cause an aging of the engine oil. A controlled aeration of the crank case therefore also slows down the aging of the engine oil.
The ventilation of the crankcase in the same way as its aeration need not be realized immediately at the crank case. Rather, the blow-by gas may be guided e.g. through the cylinder head and the cylinder head cover for different reasons. In this case, these parts, such as cylinder head and cylinder head cover, are in fluidic communication with the inner space of the crank case. It is then also possible to vent the blow-by gases from the cylinder head or the cylinder head cover for the ventilation. The aeration may be realized via the cylinder head cover or the cylinder head or via another part in fluidic communication with the crank case, too.
The pressure conditions both in the crank case and in the intake section strongly depend on the respective operational condition of the internal combustion engine. The operational condition of an internal combustion engine may, as an example, in particular be distinguished between the two states full load condition and partial load condition. Several criteria are suited in order to distinguish between full load operational condition and partial load operational conditions, each of which can be used dependent on the requirements given. It is for instance possible to distinguish the full load operational condition as operation with maximum torque and partial load operational condition as idle operation. A further possible criterion of distinction is that under full load operation, the throttle flap is completely opened, while under partial load operation, it is completely closed or only slightly or partially opened. A further possible criterion is that the supercharger of the engine is active under full load operation condition.
For these different pressure conditions of the internal combustion engine as a whole, it has to be provided that the ventilation and aeration of the crank case maintains the pressure conditions in the crank case within the limits allowed and that further, the occurring blow-by gases are guided to the intake line to a sufficient degree.
It is further necessary that the ventilated blow-by gases additionally are cleaned from oil mist and oil droplets prior to being fed back into the intake section.
For this reason, in the state of the art, for the different pressure conditions under partial load and full load, one uses ventilation devices which in sections are separated. In particular, different air-oil separators are provided, which each free the blow-by gases of the internal combustion engine from oil mist and oil droplets either under partial load or under full load conditions.
The duplicate arrangement both of the parts required for the ventilation and of the parts required for the aeration, such as air-oil separator, blow-by bypass around the air-oil separator, draining devices, outlets, pipings and the like causes that in the state of the art, a plurality of parts is required for the crank case ventilation and crank case aeration. This results in high tooling expense for the production of these parts, a high mounting expense both with the producer and at the final installation and a very large number of tubes. The cost related to this is therefore considerable, too.
Such a state of the art is for instance illustrated in DE 20 2004 011 882 U1. In this state of the art, a crank case is connected with an air-oil separator and a resonator space. Starting from the resonator space, two tubes lead to the intake section of the engine where one of the tubes opens out ahead of a turbocharger with respect to the flow direction of the fresh air and the other one of the tubes opens out downstream of the turbocharger in the intake section of the combustion engine.
In this state of the art, the aeration of the internal combustion engine is realized via an aeration line, which behind the turbocharger branches off from the intake section and leads into the cylinder head.